The overall efficiency of an internal combustion engine depends, among other things, on the amount of fuel that can be burned in a cycle. In recent years, environmental considerations have had an increasing effect. For example, the air/fuel mixture fed into the engine is typically adjusted to prevent complete combustion so that the catalytic convertor will be able to reduce emitted nitrogen oxides to a level that satisfies air emission standards. However, since such an adjustment prevents complete combustion, it results in increased emissions of unburned hydrocarbons and carbon monoxide.
In the past, a large number of systems have been proposed for improving the combustion efficiency. One approach has been to increase the oxygen concentration in the air/fuel mixture, but there are major disadvantages to this technique; the increased oxygen concentration increases the peak temperature in the combustion chamber, and thereby increases the emissions of unwanted nitrogen oxides.
Another proposed approach has been to decrease peak temperature and reduce nitrogen oxide emissions by adding water, usually water vapor, to the combustion chamber. This approach also has disadvantages; in particular, it can result in less complete combustion and thus increase the emissions of unburned hydrocarbons and carbon monoxide.
There remains a need for a system that enables both an increase in the amount (e.g., percentage) of the fuel burned per cycle, and a simultaneous minimization of the amounts of hydrocarbon pollutants, nitrogen oxides and carbon monoxide emitted.